SC627
LED Light Management Unit
Charge Pump, 4 LEDs, 700mA Flash LED,
Dual LDOs, and SemWireTM Interface
POWER MANAGEMENT
Features
Description
The SC627 is a high efficiency charge pump LED driver
using Semtech’s proprietary mAhXLifeTM technology.
Performance is optimized for use in single-cell Li-ion
battery applications.
Input supply voltage range — 3.0V to 5.5V
Charge pump modes — 1x, 1.5x and 2x
Four programmable current sinks with 32 steps from
0.5mA to 25mA
Flash LED — 700mA max in flash mode, 250mA max
continuous for spotlight
Two user-configurable 100mA low-noise LDO
regulators
The charge pump provides backlight current in
conjunction with four matched current sinks. It also can
supply continuous or bursted current to a flash LED using
the dedicated flash driver current sink. The load and
supply conditions determine whether the charge pump
operates in 1x, 1.5x, or 2x mode. An optional fading feature
that gradually adjusts the backlight current is provided to
simplify control software. A flash-timeout feature disables
the flash if active for longer than 1 second. The SC627 also
provides two low-dropout, low-noise linear regulators for
powering a camera module or other peripheral circuits.
Charge pump frequency — 250kHz
SemWireTM single wire interface — up to 75kbit/s
Backlight current accuracy 1.5ꢀ typical
Backlight current matching 0.5ꢀ typical
Programmable fade-in/fade-out for main backlight
External flash control pin to sync with camera
Optional 1s flash time out
Automatic sleep mode (LEDs off) — IQ = 100μA
Low shutdown current — 0.1μA (typical)
Ultra-thin package — 3mm x 3mm x 0.6mm
Fully WEEE and RoHS compliant
The SC627 uses the proprietary SemWireTM single wire
interface. The interface controls all functions of the
device, including backlight and flash currents as well as
two LDO voltage outputs. The single wire implementation
minimizes microcontroller and interface pin counts. The
flash/spotlight output is triggered via either the SemWire
interface or a dedicated pin.
Applications
Cellular phone backlighting and flash
PDA backlighting and flash
Camera I/O and core power
In sleep mode, the device reduces quiescent current to
100μA while continuing to monitor the serial interface.
The two LDOs can be enabled when the device is in sleep
mode. Total current reduces to 0.1μA in shutdown.
Typical Application Circuit
MAIN BACKLIGHT
FLASH
VIN
VOUT
VBAT
SemWire
Interface
Flash
COUT
4.7μF
SWIF
FLEN
CIN
2.2μF
SC627
Control
BL1
BL2
BL3
BL4
FL
BYP
CBYP
22nF
GREF
AGND
PGND
VLDO1 = 2.5V to 3.3V
LDO2 = 1.5V to 1.8V
LDO1
LDO2
V
C1+ C1- C2+ C2-
CLDO1
1.0μF
CLDO2
1.0μF
C1
2.2μF
C2
2.2μF
US Patents: 6,504,422; 6,794,926
1
June 27, 2007
© 2007 Semtech Corporation